This proposal is directed towards the key area of understanding the functional behavior of hemoglobin on a molecular basis. An attempt is being made to study the ligand combination and dissociation processes in terms of the specific structural features of the heme pocket, i.e., the role of the structural features of the heme pocket on the proximal side of the heme, on the distal side of heme, and the porphyrin related structural features. The human hemoglobin mutants (Hb M Iwate alpha F8(87) (His yields-Tyr), Hb M Hyde Park beta F8(92) (His yields Tyr) and other M hemoglobins) selected for the present study are all of clinical significance. In addition to this, studies will also be made on normal hemoglobin and some model compounds. The project offers the prospect of understanding the differences encountered in the behavior of O2, CO and NO with normal hemoglobin. The project will also provide kinetic data on the partially saturated intermediates and the role these species may play in determining the function and physiological behavior of normal hemoglobin.